Sorry for the confusion. This is correct -- it should only list "NativeCPU" and "ManagedCPU." Here's an explanation from our physics developer:

Quote

"As to native vs managed, managed means the c# implementation of the nbody code while native is the c++ implementation (not user friendly names, I know), which still has managed collision-resolution parts, though. Native is generally some 3-5 times faster, and should be the default mode. The nbody code is currently being re-re-rewritten to be even more pure c++, with still better performance, while dropping managed mode entirely.

Currently we are not using the gpu for computations. We did a long time ago use OpenCL for the core of nbody, but with support for multiple platforms, and now even mobile, the pure cpu implementation won out. This is likely to change eventually, but we will not provide gpu computation any time soon.

Sorry for misleading you, that certainly was not our intention. As you can see, those forum posts are more than 2 years old. We try to maintain accurate information in all of our marketing material, and I don't believe we state that we use GPU computation anywhere aside from these forum replies, which were true when written (I just removed the irrelevant information from the Linux troubleshooting post).

We are an Early Access game in active development, and features are bound to change. As our physics developer said in that quote, we once supported this, but CPU implementation proved the better path for now. Our new "Native Physics" on the CPU is actually much faster than our old GPU implementation ever was, mainly because more of the code runs on fast C++, where previously only the gravity actually ran on GPU, while everything else was on slower C#. It's possible we'll be able to move to some GPU computation again in the future, but so far it's only been an improvement on our old system.